The Switch
by Spazz Komo
Summary: Len and Rin finally confessed their feelings for each other and became one. However, when they wake up, they find their blossoming love may have brought along some unexpected changes to their bodies. Contains gender swap, twincest, and a lemon.


**Kagamine Rin & Kagamine Len**

**The Switch**

* * *

A/N: I'm not sure whether this had just not been done, or I just skipped over it, but I'm surprised no one had thought of this yet, rated M or not. I just randomly got this idea while reading a fic that had Rinto in it, which also featured gender swap (I'm sure it's obvious which fic that is since it's rather new. I recommend it if one hasn't read it). I've always wanted to make a Len x Rin fic, but this idea just appealed to me enough to motivate me. I hope you enjoy.

((This means English.)) Despite the gender swap, I will continue to refer to Rin and Len by their original genders (e.g. Rin is still she and her; Len is still he, him, his).

Warning: This fic contains gender swap, twincest (if you can really call it that since their androids), and a lemon. If you don't like any of those things, I suggest you don't read on.

Disclaimer: Rin and Len Kagamine, along with all the other Vocaloids in this story, are registered to Crypton Future Media. Rinto and Lenka are not characters of my own. The only thing that belongs to me is the plot.

* * *

Len's eyes fluttered open. He felt the gentle breathing of his sister on his neck, a sensation that made him want to stay there forever. A blissful sigh escaped his lips as he began to recall the previous night's activities. He and Rin had confessed their love for one another and became one for the first time. A smile formed on his lips as he looked down on the familiar head covered in those sweet golden locks snuggled up next to him so affectionately.

"_Len… Ngh…. Ah…" the blonde moaned as Len gently kissed and nipped at her neck. Her fingers tangled themselves in his similar strands of hair. For years these increasing passions built up for this moment, their love budding as soon as their bodies began to change, no longer making them like twins. They had become like strangers, having to be split into separate beds and, eventually, rooms. This, however, did not break their closeness, and unintentionally morphed their relationship of brother and sister into that of lovers._

_Their fingers intertwined as Len slowly pushed through. Rin yelped a bit in pain, not yet used to the feeling. A flurry of emotions – fear, lust, love – swirled wildly inside her heart, making her it pound rapidly and small tears swell up in the corners of her eyes. He calmly whispered to her, kissing her tenderly on the cheek, reassuring her. With a firm nod from his partner, he began…_

The memories of that moment still rang on loud and clear, and it was definitely something neither of them would forget. _"Hmm… What time is it?"_ He rolled over carefully, trying not to stir her awake. 7:34 – good, it was still early enough for him to get back to his room. Placing a gentle peck on Rin's head, he slowly shifted off the bed.

He quickly pulled on his boxers before simply picking up his other clothes. He took one more look back, savoring the image of Rin sleeping before leaving. The door barely made a creak as he closed it and dashed across the hall. Before he knew it, he was back in his room. His breath was ragged since he had been holding it the whole time he made the cross, but he felt nothing but relief. He had made it.

The clothes in his arms dropped to the floor as he collapsed onto his bed. He couldn't help but notice that Rin's was much more comfortable than his, but that was obviously an issue he wouldn't bring up anytime soon considering how he figured it out. Laughing silently at his own mental bicker, he lifted himself back up and walked over to the bathroom that was connected to his room. After last night, he did feel the need to shower, plus it would help him wake up.

With a yawn, he lazily discarded the clothing he had rushed to put on not even ten minutes ago. The water gained warmth rather quickly, and he entered the shower. "Ah," he breathed happily, splashing handfuls of the soothing water on his shoulders. The steam surrounded him, somehow lifting the weariness off of him.

After standing under the running water for what he dubbed long enough, he grabbed the bar of soap and began to wash off. First around his neck, over his shoulders, down his arms, then his ch- Something was off. As he ran the bar of soap over that some area, he felt a rather large bump – two to be exact. He looked down with concern. _"What the-"_ Len was stunned. _"Wh-what the hell!?"_ His eyes were as wide as ever as they stared at what he found. A pair of breasts. But how? Len was a man, and men most certainly did not have chests like this. He rubbed his eyes numerous times, hoping this was some hallucination caused by his fatigue, but, no matter how many times he did it, they were still there. The only other thing he could think of was that he was dreaming. He pinched his arm multiple times, increasing the intensity of each pinch every time he didn't wake up. It was of no use. He wasn't dreaming or hallucinating. He clearly had a pair of breasts. He couldn't explain how, but there was no point denying what was true.

"_Wait…"_ A strange thought popped into his head, and he felt the immediate urge to check if… "Oh my god…" he groaned. He not only grew breasts, but he had completely changed into a girl. His precious manhood had been replaced with... well, that. He even noticed that his voice was much higher in comparison to how it sounded yesterday.

He quickly washed the bits of soap of his person before shutting off the water and lunging out of the shower. Staring at himself in the mirror, Len mentally slapped himself for not noticing it earlier now that he saw just how obvious his change was. The breasts weren't the largest in the world – larger than Rin's at least – and he most definitely had a… yeah. "What the fuck!?" he cried out in his now girly voice.

He gawked at the mirror in complete bewilderment as his hands traced over his new feminine features. Not only had he gained girls parts, but his body was that of a girl's as well. His cheeks had filled out, his chin was much pointer, his hips curved out, and his waist curved in. He couldn't even recognize himself anymore.

"How could this have happened?" he voiced aloud to himself, wrapping a towel at first around his waist, then, after careful consideration, around his whole person. He trotted out the bathroom and plopped onto his bed. No matter how much he thought about it, nothing seemed to make sense, which it really didn't. Squishing his hand against his breast to prove that they were really real, he sighed in defeat. What the hell had happened?

Len simply sat there, trying to solve something that he was doomed to not understand. His train of thought was soon interrupted by a somewhat low pitched "Eep!" coming from across the hall – from Rin's room. He quickly sprang up ready to rescue his love, but as soon as the towel hit the floor, leaving his naked body victim the cold, he figured it would be a good idea to put clothes on first. He retrieved a fresh pair of boxers, a clean white t-shirt, and a pair of his trademark shorts, throwing them on before finally dashing out of the room.

"Rin!" he called out, bursting through the door at full speed. This, however, didn't faze the already stunned girl, frozen in her deadpan stare under the lifted blanket. She had also been changed. Her once budding breasts, which she was so determined to grow, were now as flat as ever, much to her dismay. Rin couldn't help but notice that she had grown a rather noticeable new appendage. Just looking at what had happened completely shut her down, her face growing blue because she had apparently stopped breathing.

Len ran up to her, jostling her enough to snap her out of it. "L-L-Len…? I-is that you?" Her voice was much more masculine than how it was before. Not to mention that she looked like a guy with her larger physique.

"Unfortunately, yes. It's me Rin," he tried to say in his normal husky manner, though it came out rather pathetically in his new voice. Rin's hands shot out, smooshing his cheeks together in disbelief. "R-Rin, what are you doing?" he swatted her hands away, "Stop that."

She shook her head frantically, "What happened? You've become a girl, and I'm a dude! Am I dreaming or something?" she gushed rather quickly, pinching herself numerous times on the cheeks. Len grabbed ahold of her hands just as they began to leave red marks on her face. "Don't bother, I've already tried," he grumbled, showing her the red marks that formed all over his arm.

He sat down beside her on the bed. They both had the same look of fear and concern on their faces. Neither of them understood why this happened. Was it because they had sex or something? Was this their punishment from some greater power for loving each other? "Len, are we going to be stuck this way?" Len didn't want to answer. What he wanted to do was hold Rin in his arms and gently pet her head, whispering in her ear that it would be alright like he did before. But he couldn't do that, because he wasn't even sure that it was going to be alright – and it was much more difficult to do that when she was currently bigger than him.

Suddenly, they heard a knock at the door. "Rin-chan! Time to wake up." It was easy to tell who that sticky sweet voice belonged to

"I'm already up, Miku. Just getting ready," Len responded, somehow figuring out quickly what would happen if Rin responded with her more boyish voice. Rin looked at bit confused, but then she understood and mouthed the words "thank you" in his direction.

"Alright-y then," Miku responded merrily. They waited until they could no longer hear her footsteps going down the hall until they began to talk again.

"This is bad. If we tell the guys what happened, they'll just ask us if there was anything we could have done to cause this, and then we'll have to tell them about our relationship. Even if they can help us, they'll never let us see each other again," Rin exclaimed rather frankly. Nevertheless, she wasn't wrong. There was no way to explain their case without having what happened last night come up, seeing as it honestly could have been the cause for whatever reason.

"Then I guess we'll just have to wait until this changes back just as spontaneously as it occurred," Len replied with a sorrowful nod. "Until then, I guess we have to switch places. I'll wear your clothes, and you'll wear mine. We don't look exactly like each other, but it's close enough. Miku even thought my voice was yours, so _maybe_ it'll work vice versa." Rin smiled a little at Len's reasoning, finding his implication of Miku being gullible humorous.

"O-okay. I guess that could work for as long as this lasts." She began to move from under the blankets before she remembered just how much she changed. Len stood up making room for her to get up but noticed that she stopped.

"What's the matter?"

"Well, it's kind of embarrassing…" She wasn't afraid to show her body to him, but now that she was a guy, she felt a whole new feeling of self-consciousness.

"Ah, don't worry about." He forced a little laugh. "I've been a guy up until now, so it's not like I haven't seen anything." He was pretty hypocritical at this point. He was well aware at seeing one's own self naked and seeing someone else naked, even if they were the same gender as you. Hell, he was embarrassed to start undressing right there so he could give Rin his clothes. Rin had gotten up just as he removed his boxers, and he turned around to hand them over to her.

"Here you g-" Len paused for a minute taking in her new body. She seemed much more developed than he ever was, and he couldn't help but notice that she was _bigger_ than him, too. A blush coated his cheeks and he bit back the anger he felt over that. It wasn't much different for Rin, either. Len's new breasts were the ones she had wanted for so long. Biting her tongue, she took the clothes from him.

"Thanks," she responded, holding each piece daintily like it was something she had never seen before. She slipped the boxers on and soon was fully dressed. Satisfied with how well they fit, she looked up at Len who was still standing there in the nude. It dawned on her that Len had no idea where she kept her clothes, and she walked over to her dresser. A pair of pink panties, a bra, a pair of shorts – longer than the ones she normally wore – and a light blue shirt seemed satisfactory, and she hurriedly handed them to him. Len managed to get on the panties without any trouble, as expected, but the bra had him dumbfounded. Pulling the straps on, he didn't know how he was supposed to reach around and hook the back. Rin rolled her eyes and helped him by hooking up the back. Another bit of anger came up when she noticed that the bra was far too small for his breasts. Len, however, didn't notice and continued getting dressed. Rin handed him her clips, and, in return, Len gave her his rubber band to tie her hair up.

"Well, I guess I'm Rin now," Len chuckled awkwardly. "And you're Len. I guess that makes me the older one." Rin playfully punched him in the shoulder for that remark but soon regretted it, recognizing that this was a bit more painful now that she was stronger and he was weaker.

"Oh, sorry. I guess I don't know my own strength yet."

"It's alright." He rubbed his shoulder a bit, before punching Rin right back in the same manner she would have. With that they both exited her room, making sure no one saw them leaving at the same time. Everything seemed to be going good so far. That is until they entered the kitchen.

"There you two sleepy heads are!" Meiko chimed turning around to place some more pancakes on the table. It was then that she paused to inspect the two. Had they been figured out that easily? She seemed surprised to see them. "Whoa! Have you two always been this big? It's like you sprung up overnight," she bellowed, patting them both on the shoulders. The brunette snickered again, seeing how flustered they became and went back to taking out the last pancake from the skillet.

Kaito looked up from the television in the connecting living room and appeared a bit astonished himself. "Wow, Meiko's right. Rin's even grown those breasts that she wanted." Len had to restrain Rin from pummeling him, mainly because she was him at the moment. Meiko had dashed from her place at the table and smacked the skillet across the back of Kaito's head in retaliation anyway.

"Don't say perverted stuff like that to Rin," she growled bitterly. Seeing that it had been justified, Rin finally calmed down, thanking Len silently again. He mouthed a "no problem" back at her, and they took their places at the table.

Miku, who had been chopping a leek on her plate, finally acknowleding what was happening around her after she finished cutting each slice precisely. "Did you guys switch roles or something?" Len nearly choked on his orange juice when he heard her comment.

"Wh-wh-wh-what do you mean, Miku?" Rin quickly asked, not quite ready to turn herself in yet.

Miku giggled. "Well you usually sit in that spot, and Rin usually sits there. Not saying there's anything wrong with that. Just thought it was funny," she waved her hand casually, not sure what the panic was about.

"Oh, right. I never noticed that. Hehe…" Len responded. Both exchanged nervous looks before going back to fixing their plates. Rin piled a large stack of pancakes on her plate and began eating them as fast as ever. Len, on the other hand took two of them, cut them into bite sized bits, and ate them quietly.

"You two sure have changed," Meiko remarked, dragging Kaito's almost lifeless body into a chair before sitting down next to him. "Usually Rin would be scarfing down the food, and Len would be more conservative. I guess that's just how the body changes, huh?" Another mistake. Too many of those and they would surely get suspicious.

"Oh, yeah, that's it, I guess." Len took another bite of his pancakes, and basically remained quiet. Rin did the same, though she didn't act any different from how she normally did.

As breakfast came to an end, the two quickly dismissed themselves. Figuring it wasn't safe enough to go into either one of their rooms, they retreated to the garden in the backyard. Not the most private of places, but going there together wouldn't look too peculiar. Figuring that their best bet was to just not be around the others, they went about their normal chatters – talking about their relationship, new songs, and other little things – and enjoying each other's presence.

"This whole thing is so weird," Rin commented, catching Len by surprise. They had somehow managed to not talk about their change the entire time, but it was the elephant in the room and someone had to bring it up.

"Yeah." There wasn't much more to say than that. "I wonder if this is what we'll look like soon." He didn't notice that he was speaking his mind until Rin gave him a sly look.

"You just want to be all buff and tough like I am," she taunted, flexing her muscles ostentatiously. Len stuck out his tongue, trying to dismiss how dead on she was.

"W-well, you're all jealous of my boobs, which make yours look like they were ran over by the roadroller," he snickered, posing in a manner that made them stick out more. Rin's face flushed as red as a tomato.

"Not unlike you. I know which part of this bod you're most jealous of," she said rather hotly. While this was their style of teasing, which they both found very amusing, the awkwardness of it all seemed to fly right over their heads. Anyone else listening along could most likely only manage a deadpan expression as they continued to speak so lewdly.

"W-well you… You're just… Because of…" Len couldn't manage any other comebacks, having his best one shot down by yet another critical shot.

"Hah! I win!" she shouted, jumping and pointing mockingly at her brother – well, sister. She burst into a fit of giggles, very unfitting of her current appearance. Wiping a tear from her eye, she noticed that Len's face was even redder than hers as he looked away and pouted. "Oh, come on. It's not that big of a deal." She checked to make sure no one was coming then leaned next to him seductively. "I still think you're pretty big."

Whether or not it was possible for his face to get anymore hotter than it already had, one could literally feel the heat radiating from it. His voice caught in his throat, choking out his words. "R-Rin!"

Rin wrapped her arms around his neck and pressed their foreheads together. "Call me Rinto…" she purred, lowering her voice just enough to send shivers down his spine. She twirled her finger through his hair, kissing the end of his nose.

"U-uh… Rin… to," Len started, trying not to completely melt in her arms. Before any other word came out, Rin placed her lips over his, silencing him instantly. He let out a muffled moan. Strangely, this situation reminded him a lot of the night before – of course, the roles were switched. As he went to pull back and mention that, Rin leaned further into the kiss, maneuvering her tongue until it had invaded the smaller Kagamine's mouth. Len no longer tensed up but, instead, retaliated, moving his tongue along with hers.

It wasn't long until Len gave in, knowing that Rin was in the dominant position for the time being. They pulled back to return air back into their lungs, though she still continued to press their foreheads together, trying to stay as close as possible.

"Rin! Rin-chan!" Luka came out into the garden, heading right towards them. The real Rin's demeanor changed completely. The seductive glint in her eye returned to her normal, devious shimmer.

"Good luck with that sexual frustration while shopping with Luka," she whispered with a wink. She perked up, making a more conventional space between them. "Oh, hello, Luka-nee."

"Hello, Len." The pink haired girl sent a small wave her way. "You ready to go on our shopping trip, Rin-chan?" Len's face sunk as low as it could go. As a guy originally, there was nothing he hated more than shopping.

"O-oh, right. I nearly forgot. Ehehe… Yeah, I'm ready," he sighed, rising up and staring daggers at his grinning sister. She would most definitely pay for that later. He wasn't sure how yet, but she would pay.

"Hmm…" Luka hummed, eyeing him over now that she could see him fully. Without warning, she shamelessly groped his breasts, causing him to squeak. This actually shocked Rin, making her jaw drop. Before saying anything, Luka squeezed them a few times then nodded. "Looks like we need to buy you some new bras. You're chest grew. ((How magnificent!))" Len just stood there, feeling embarrassed and violated. Rin, snapping out of her daze, burst into laughter as Luka dragged away the mortified Len. One could only imagine how hilarious the sight of Len trying on bras would be.

* * *

It was late in the evening before, Rin and others heard Luka burst through the door with what seemed like a thousand shopping bags – realistically, it was only ten. "((Hello, hello, my whimsical kinfolk~!)) I had quite the shopping spree with Rinny. She even got some new underwear." Upon hearing this, Kaito perked up noticeably, quickly receiving a smack from Rin, in defense of herself and of Len.

It took Miku a moment to register that Luka had once again mixed her languages, and then she jumped up and peeked through the bags. "Wow, Luka-nee. You got so many cute things. I wish I could've gone with you instead of heading to the recording studio," she groaned. Ironically, it was all the recordings that she did that made it possible to go on such a rave shopping spree, but no one bothered to bring it up.

Len trotted in heavily, the blankest of expressions across his face. The only real show of emotions was the burning blush painted on his cheeks. Rin snickered. It was obvious which store caused that look. Luka tossed him two bags with his things in them and went back to basking in Miku's jealously as she pulled out each individual outfit she had bought for herself. He moved his head slightly in what appeared to be a nodding motion and stomped down the hallway to Rin's room, Rin following closely behind him.

As soon as he entered the room, he completely let loose. "Oh my god, Rin! How can you stand it!? Going shopping with her is unbearable. I mean shopping in general is bad, but… GAH! Four hours of 'Oh look at this!', 'I thought this only came in such and such colors!', and (('Oh, dearest Rinny,)) this would look positively perfect on you; you must try it on'. I swear if the mall hadn't closed, we would've never left," he cried out in one long sitting, finally collapsing on the bed to catch his breath.

Well aware of how Luka's shopping trips progressed, Rin ignored her brother's whining and dug through the bags. "Yeah. Right. No one besides Miku wants to shop with her, and when Miku's busy, she cons me, Meiko, or Gumi into doing it… She actually picked up some really sweet shirts, and these pants are pretty nice, too." Finishing her pillaging through the first bag, she moved to the other one. Hmm. A bra – what do you know, Len's only one cup larger than her. There was a pair of matching panties. She snickered. Digging a bit deeper, she pulled out rather revealing pieces of lingerie. Even her face turned red.

Len sat up when he had heard the rummaging had stopped. "O-oh. I forgot to mention. Luka thought that you're dramatic growth spurt meant you were ready to transition from being all cutie to dressing more sexily. I tried to talk her out of it, but she insisted I get at least one thing like that." It was silent. Rin just continued staring at it in disbelief. Now that she thought about it, Len would look pretty nice in it. Rin wasn't into girls, but it must've been the gender swap that gave her the sudden change of interest.

"Did you… Did you try it on? D-does it fit and everything?" The question sounded a bit awkward at first, but Len strangely enough had no problem answering. Maybe this switch did more to their personalities than they had original thought.

"Well, of c-course. If it didn't, we wouldn't have bought it." Rin only mustered a slight nod.

"O-oh…" The silence consumed the room again. They had both froze in place, Rin still holding the matching bra and panties set, and Len matching her stare. It seemed like at any moment one of them would say something, but each time it was only a false alarm.

"Rin, dinner is ready." The sound knocking finally broke the silence like a hammer smashing into glass. The caring sound of the older brunette – which was used about as often as her harsher tone – jolted them out of their stupor. "Oh, and if you know where Len wandered off, too, tell him." The footsteps echoed down the hallway, and they felt it was safe to speak again.

"Welp, I guess it's time to go eat," Rin chimed, putting the clothes back in the bag like that whole instant never happened. She rose up rather stiffly, however, as she stepped loudly out of the room. Had Len… won? He wasn't quite sure he did anything, but it appeared to be Rin who was silent this time around. He glanced into the bag, seeing that outfit lying there on the top. Maybe he could use this to his advantage.

* * *

Rin sat down, this time in Len's original seat. Luka was sitting next to her, a dreamy look on her face as she watched Miku chop up yet another leek with complete drive and precision. She sighed happily, her gaze not faltering from the other girl. _"What's this all about?"_ Rin pondered, having not noticed Luka's staring since Len was normally blocking her view from it.

Meiko, placing the final plate of food on the table, nonchalantly smacked Luka across the back of the head with the serving spoon before placing it on the plate. The pink haired girl, somehow not reacting to the pain from the force of the whack, sat up promptly, her eyes still on Miku but not as focused as before.

Len wandered in just as Meiko sat down. "Well, hello. I honestly expected Len to get here after you," Meiko remarked snidely, unaware of how accurate her guess was. "Oh, well. Sit, sit. Let's eat then." Len nodded and sat down in Rin's spot. Rin looked over at him, pointing back at Luka with a puzzled look on her face. Len mouthed the words "don't ask", before reaching for some food.

Dinner continued on as it always did. Everyone talked about their day, which for most was very uneventful. Meiko had no plans, so she spent all day with Kaito watching TV and cooking. Kaito, also having no plans that day, just ate ice cream and watched TV, not doing anything productive at all. Miku had recording all day and Luka only had it in the morning, leaving her afternoon open for that extensive shopping spree with Len.

"I even got to see Miss SeeU record a song when I walked in," Miku giggled, her cheeks turning a bit pink at the mention of the Korean Vocaloid. Luka's grip tightened on her utensil, bending it slightly. The teal haired girl, however, was oblivious to this and placed more slices of leek on her food. Rin elbowed Len once again, asking what the hell was going on – without actually shouting it of course. Len still didn't bother over it, telling her he would tell her later.

"Mm-hm, sounds very exciting, Miku," Kaito commented, still feeling a bit too lazy to come up with a proper response. The meal had been finished, and everyone still sat around chatting it up. Kaito was the first to dismiss himself, aiming for his room so he could sleep off the food, but Meiko promptly grabbed him by the scarf, kindly suggesting that he help her with the dishes, a threatening tone disguised in her voice. Len then got up, as well, heading somewhere in a bit of a hurry.

"I wonder what's up with her," Miku commented, now just casually munching on a leek. Luka shrugged, looking to Rin for any answers.

"I dunno," was all she could muster, not sure what her brother was up to either.

* * *

Everyone sat around the TV, watching the music channel to see if any of them had been mentioned or one of their songs was shown. Of course, Miku was mentioned once or twice, along with Meiko, surprisingly, and a few songs by some of the new Vocaloid 3s. It didn't take long for most of them went their own ways, though, Rin stayed to watch just a little bit more.

Finally, growing weary, she turned off the TV and walked to her room. "Oh, that's right. I guess I need to sleep in Len's room, huh?" she said, as she opened the door. Strangely enough, Len wasn't there. "He probably just didn't remember that." It was completely unlike him to not remember something this, but it wasn't beyond him. He was a human, too – well, a human-like android.

"Len, are you in here?" Rin whispered, opening her brother's room. It was dark, to say the least, so her hand traced the wall looking for the light switch. What she found as the lights flashed on was not what she had expected at all. There was Len, lying on the bed, posed so his whole front faced the door, dressed in that oh so sexy lingerie.

"I've been waiting for you," he cooed with a wink. He got up and strutted in her direction. By this point, her face was crimson red, and her eyes followed Len's every move. Len pressed himself against her, trying to get as close as possible. "You know you really do spend too much time watching TV, Rinto." Rinto? Who was… oh right, from their little make out session earlier. Did this mean that they going to…

"L-Le-" Rin began before Len pressed his lips to hers, muffling out the rest of what he was going to say. Rin began to lose the feeling in her legs, about ready to give into him, but then she thought about something. This was almost exactly like what happened before. Was Len only doing this to get back? Was he going to kiss her passionately then just leave her right before anything could really happen? Like hell he would!

Rin took over the kiss, kicking the door shut with her foot before wrapping her arms around Len's smaller body. She noticed that he tensed up, obviously not expecting for her to catch on that quickly. He still tried to claim dominance by prodding his tongue into her mouth. Rin responded positively, her tongue moving around with his, as she slowly moved him back to the bed. They both collapsed back onto it, Rin falling on top of her feminine brother. The kiss broke, and they gasped for air, staring into each other's flushed faces. This would be the point where Len made his escape. Where he'd casually brush this off like it never happened and head to bed, right? Wrong. As he started to wiggle free, Rin pinned his arms to the bed.

"You won't get away that easily," she hummed in his ear, making him tremble. Her tongue traced down his jawline. She placed little nips on his neck, not wanting to mark him up, but to just tease him a little. Len, squirming each time she went over those light marks with her tongue, did not expect his little trick to go this far. His leg inched up, his knee coming in contact with Rin's groin. She groaned audibly, not sure what had caused her to do that. Trying not to become distracted, she moved down to Len's collarbone, acting like it hadn't fazed her. Len, however, noticed. He pressed his knee against the sensitive region between her legs.

"Wh-what are you doing?" she whispered hoarsely, trying not to buck up against his leg. Len smirked deviously, his face still looking desperate for Rin's advances.

"I'm surprised you can't recognize when you have an erection, Rinto," he snickered, rubbing his knee across that spot again. Rin bit her lip, suppressing another moan. If Len was going to play that card, then she would have to play her own.

A wicked grin spread across her face as Rin grabbed Len's breasts suddenly. He squeaked in a manner similar to when Luka groped them earlier. Instead of simply feeling them, though, Rin began to knead them gently, causing him to be reduced to a fit of pleasure filled noises. "Aw, little Lenka, likes being felt up, huh?" Rin pulled down the straps, allowing his breasts to be freed from their cups. She wasn't quite sure what to do, but, remembering what Len had done yesterday, she placed her lips around one nipple, her other hand still squeezing the other. Len, having never felt this kind of sensation, fell absolutely helpless under her touch. He could barely muster enough willpower to continue teasing her, but he wouldn't be beaten.

Len's hands snaked his way up her shirt, gently running his fingers from her chest to her stomach, making her let up just enough to let him slip away. He bucked up, flipping the two of them over so he could straddle Rin. By now the bulge in Rin's pants was very noticeable, and even she blushed at the sight of such a thing on her.

"Let's have a little fun with Rinto's new appendage," he purred, grinding against the clothed erection. Rin grunted, trying to match the sensation in time with Len's movements. Though he tried to keep a straight face, Len even had to admit that it felt really good. If he progressed, then he would be left open for Rin to make her move. He hastily stopped, shifting off of Rin, much to her protest. "Now, now," he hummed, moving between Rin's legs, "Don't get fussy." Rin pouted. How dare he talk to her like she was a child, especially at a time like this! She eyed him, wondering what he was going to do, though, in all honesty, it was pretty obvious.

Len undid Rin's shorts and pulled down her boxers, just enough to free her cock and let it stand there in its full glory. Even Len was taken aback by it at first. It definitely was much bigger than his – at least it looked that way from the angle he was at. Shaking his head, he wrapped a shaky hand around it. He wasn't sure what he was doing. He had done it to himself a few times – something he was ashamed to admit – so he figured it wasn't much different from that. His hand started to pump it, each time making it feel harder and harder. Rin's eyes rolled to the back of her head, mouth agape and making all kinds of different noises. Len licked from the base to the tip, stopping briefly to coat each part of it thoroughly. He felt like attempting a blowjob with no experience at all would be a bad idea, so he settled for this. It made no difference to Rin, considering how close she was.

"G… GAAH!" Rin cried out, finally reaching her limit. Her seed spread in every which direction, falling onto her shirt and on Len's face. Her breathing was strained as she began to speak. "A-ah, I'm s-sorry, Lenka…" Len wasn't bothered by it, though. He actually liked it… hell, he loved it! He began pumping her now semi-hard member again. Once it had returned to its previous state, Len sat up and looked Rin in the eyes.

"R-Rinto," he started, more embarrassed than he ever had been about saying this, "I-I want you." He sat up, pulling his panties off. The room's temperature felt like it had skyrocketed, and Rin felt compelled to remove her soiled shirt, shorts, and boxers. Seeing that Rin had completely stripped, Len also took off his bra, somehow doing it without any mess ups.

There they were, just like the night before. Left in awe of each other's fully exposed bodies. Len gulped as he positioned his entrance over Rin's cock. He stopped for a moment, his eyes connecting with Rin's. He then took a deep breath and slowly lowered himself until Rin was completely inside of him. His back arched at the feeling of being completely filled up. It was like an odd mixture of pain and pleasure, but mostly pleasure.

After adjusting to it, Len began to ride her. Seeing as it was hard for him to keep pushing himself up, Rin helped by rocking her hips in time with him. Len found it nearly impossible to contain his cries. "Ah…. A-Aaah~! Rin… Rinto~!"

Len lost feeling in his legs, not being able to keep going no matter how good it felt. Rin perked up from his stupor, seeing Len struggle to keep up the pace. She placed her hands on his hips and rolled over, not wanting to separate for even a second. Now she was on top, but their little competition from earlier had been completely forgotten by then. They stared into each other's eyes, each glazed over with pure, unadulterated lust.

Their lips met passionately, as Rin began to thrust into him again. Len's arms wrapped around Rin's neck, desperately trying to pull her as close as possible. Their bodies remained connected as Rin slammed into him, both so close to climax. "Aaah! Oh g-god, Rinto!" Len screamed as his vision turned completely white, and he reached the pinnacle of bliss. Rin soon followed, shuddering violently as the orgasm took over her whole body. Luckily these rooms were near soundproof, or everyone in the household would have heard the two of them screaming in ecstasy.

Things began to calm down as Len and Rin still lied there, basking in the afterglow. Rin had pulled out and fallen next to Len, and they both watched each other lovingly. Both wore weak smiles, and their hands latched together. "Lenka… I-I mean Len," Rin started. "I love you." The words were quiet, but they still carried the full meaning.

"I love you, too, Rin," Len responded, giving Rin another kiss. He let out a sigh as he began to drift off. Rin took the liberty of covering themselves with the blanket. She snuggled up to her brother, holding him close in her arms. Another kiss was placed atop his head, and she, too, fell asleep. Overall, what started out as a rather unusual day, ended perfectly.

* * *

A/N: I have this strange head canon that Luka likes to switch between languages, and when she speaks English she uses lots of fancy and outdated words.

Though Rinto and Lenka didn't make cameos, I thought that them using those names the way they did worked pretty well. Sorry for the whole "His precious manhood had been replaced with... well, that" and other similar lines. I don't like using the words that I used those as substitutes for. I don't feel comfortable using them despite the fact that I can write out a sex scene with even blinking. I did force myself to use the term "cock" a few times, though.

I'm not too pleased with how I wrote this, mainly because of how I overused some words. I tried my best not to do that, but I'm afraid that's just how I write. Anyway, I hope you guys liked it. Please review, and thanks for reading.

Disclaimer: Rin and Len Kagamine, along with all the other Vocaloids in this story, are registered to Crypton Future Media. Rinto and Lenka are not characters of my own. The only thing that belongs to me is the plot.


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